Method for producing a coating and optoelectronic semiconductor component having a coating

ABSTRACT

What is specified is a method for producing a coating comprising the following steps:—providing a material source having a top surface and a main coating direction,—providing a substrate holder having a top surface,—providing at least one base layer, having a coating surface remote from the substrate holder, on the top surface of the substrate,—attaching the substrate holder to a rotating arm, which has a length along a main direction of extent of the rotating arm,—setting the length of the rotating arm in such a manner that a normal angle (φ) throughout the method is at least 30° and at most 75°,—applying at least one coating to that side of the base layer which has the coating surface by means of the material source, wherein—during the coating process with the coating, the substrate holder is rotated about a substrate axis of rotation running along the main direction of extent of the rotating arm.

One object to be achieved is to provide a method for producing aconformably covering coating. Another object to be achieved is toprovide an optoelectronic semiconductor component having a conformablycovering coating.

What is specified is a method for producing a coating. The coating maybe a metal layer, a semiconductor layer or an insulating layer of anoptoelectronic semiconductor component, for example. Preferably, thecoating is a thin layer, namely with a thickness of 10 μm at most, forexample, of a material, which has preferably few impurities. That is,the layer preferably consists of the material and comprises for example3% at most, in particular 1% of foreign substances at most. Preferably,the coating is formed with a material, which can be provided by means ofa vaporization source as a material source.

According to at least one embodiment of the method, first a materialsource having a vaporization surface and a main coating direction isprovided. The material source includes, in the interior thereof, thematerial for the coating, for example. If the coating comprises multiplematerials or multiple material components, even multiple materialsources or one material source can be used with multiple materials. Theat least one material for the coating is released from the materialsource by means of heating or charged particle bombardment, for example.

The main radiation of the material source is effected along the maincoating direction. In other words, a material flow released by thematerial source is maximal along the main coating direction. Thematerial flow may be minimal in at least one extension direction of thevaporization surface of the material source, i.e. vertically to the maincoating direction.

According to at least one embodiment of the method, a substrate holderwith a top surface is provided. Preferably, the top surface has a planardesign. In other words, the course of the top surface deviates from avirtual mathematical plane, which runs through the top surface, by+/−10% at the most, preferably +/−5% at the most, of the thickness ofthe substrate holder, perpendicular to said plane.

The top surface of the substrate holder faces the material source. Avirtual extension of the top surface encloses an angle of less than 90°with the main covering direction. In the present case, the substrateholder may be a rotary disk, for example. In general, it is possible forthe substrate holder to be formed from a mechanically self-supportingmaterial. In other words, a further supporting element protecting thesubstrate holder from being damaged is not required for the transport ofthe substrate holder. Here, the substrate holder may be formed frommultiple layers, wherein the top surface of the substrate holder may beformed with a semiconductor material. The top surface of the substrateholder comprises silicon, for example.

According to at least one embodiment of the method, a base layer isarranged on the top surface of the substrate holder. The base layercomprises a coating surface facing away from the substrate holder. Thebase layer may be the element to be coated, e.g. the substrate to becoated. The coating surface faces the material source. As a result, amaterial vaporized from the material source can be applied to thecoating surface. Furthermore, the base layer preferably comprises fourside surfaces. Here, choosing the term “coating surface” shall not meanthat exclusively this surface is provided with a coating. Rather,preferably, also the side surfaces of the base layer are provided withthe coating. The coating surface rather is a main coating surface, i.e.the surface where quantitatively the most material is deposited from thematerial source, due to its position relative to the material source,and due to its geometric dimensions.

For example, the base layer is designed in the shape of a cuboid, atruncated pyramid or a truncated cone. Here, the four side surfaces mayconnect the coating surface and a bottom surface of the base layerfacing the top surface of the substrate holder. The base layer may be anot yet finished optoelectronic semiconductor component, for example.That means that the base layer may comprise layers and/or structures ofan optoelectronic semiconductor component.

According to at least one embodiment of the method, the substrate holderis attached to a rotating arm having a main extension direction. Therotating arm is attached to a bottom surface of the substrate holderfacing away from the top surface of the substrate holder. The rotatingarm is preferably fixedly connected to the bottom surface of thesubstrate holder. The main extension direction of the rotating arm runsvertically to the bottom surface of the substrate holder. The rotatingarm has a length in its main extension direction. For example, the endof the rotating arm—facing away from the substrate holder—is fixed to arotary joint. The attachment may, for example, be effected mechanicallyby means of a screw connection.

Preferably, a virtual extension of a substrate axis of rotation of thesubstrate holder runs along the main extension direction of the rotatingarm. Here, the substrate axis of rotation extends from the top surfaceto the bottom surface of the substrate holder. Preferably, the substrateaxis of rotation runs through a center of mass of the substrate holder.Here and in the following, the term “center of mass” is not to beunderstood as a geometrically exact center of mass, but merely as acenter of mass within the production tolerances. For example, the centerof mass deviates from the geometrically exact center of mass withregards to a diameter of the substrate holder by up to 15%, preferablyby up to 10%.

According to at least one embodiment of the method, the length of therotating arm is adjusted. For example, adjusting may be effected byselection of a rotating arm with a corresponding length. Furthermore,the length adjustment may be effected by means of a displacement of therotary joint in the direction away from the substrate holder or by adisplacement of the fastening point of the rotating arm on the rotaryjoint.

According to at least one embodiment of the method, the length of therotating arm is adjusted such that a normal angle is at least 30° and atmost 75° throughout the entire method. Preferably, the normal angle isat least 40° and at most 60°. Here, the normal angle is the angle whichis enclosed by a surface normal of the coating surface of the base layerthrough a sample point on the coating surface, and a sample vector. Thesample vector is derived from the connection vector from any point onthe vaporization surface of the material source to the sample point onthe coating surface of the base layer. Preferably, a point through whichthe main coating direction runs, not an arbitrary point, is selected asa point on the vaporization surface of the material source.

For example, the normal angle may be an angle which is enclosed by avirtual extension of the rotating arm in the direction of the materialsource and a connection vector from the material source to the fasteningpoint of the rotating arm.

According to at least one embodiment of the method, now, at least onecoating is applied to the side of the base layer that has the coatingsurface. Hereafter, this application will also be referred to as a“coating process” and is effected during a coating time. The coating hasa coating thickness. Here and in the following, the term coatingthickness relates to the respective shortest distance of an externalsurface of the coating facing away from the base layer toward the topsurface or toward one of the side surfaces of the base layer locatedunderneath the coating.

Application of the coating is effected via the material source. Forexample, the coating is applied by vapor deposition by means of thematerial source. Coating is effected during a coating time, wherein saidcoating time is preferably selected to be so long that a completecovering of the coating surface and/or the side surfaces of the baselayer results. Here and in the following, the term “complete covering”of the base layer means that all exposed external surfaces of the baselayer facing away from the substrate holder are no longer freelyaccessible after the coating and that the entire surface is covered bythe coating. Thus, the coating is particularly a closed layer and doesnot comprise multiple materials, which are not interconnected withmaterial of the coating.

According to at least one embodiment of the method, the substrate holderis rotated around the substrate axis of rotation during the coating ofthe at least one coating. Rotation is preferably effected with aconstant rotary frequency. In other words, the rotary frequency is notchanged during the coating time and the coating process, respectively.The substrate axis of rotation runs along the main extension directionof the rotating arm. Preferably the rotating arm is rotated arounditself. The self rotation of the rotating arm can be realized with therotary joint, on which the rotating arm is attached, for example.

Here, it is to be observed that the normal angle varies during thecoating process due to the rotation of the substrate holder. The reasonfor this lies with the fact that the substrate axis of rotation, alongwhich the rotation is effected, generally does not run through the baselayer. With respect to the position of the substrate axis of rotation,the base layer is closer to the material source at the start of theproduction method, for example. Due to the rotation and with respect tothe position of the substrate axis of rotation, the base layer islocated farther away from the material source at a later point in timeduring the coating process. The distance of the base layer to thematerial source varies over time due to the rotation around thesubstrate axis of rotation. This results in a change of the samplevector and thus a change of the normal angle. Despite the variability,the normal angle is at least 30° and at most 75° throughout the entireproduction method.

According to at least one embodiment of the method for producing acoating, the method comprises the following steps:

-   -   providing a material source with a top surface and a main        coating direction,    -   providing a substrate holder with a top surface,    -   providing at least one base layer with a coating surface facing        away from the substrate holder on the top surface of the        substrate,    -   attaching the substrate holder on a rotating arm, which has a        length along a main extension direction of the rotating arm,    -   adjusting the length of the rotating arm in such a way that a        normal angle, which is formed by the surface normal of the        coating surface of the base layer through a sample point on the        coating surface and a sample vector, derived from the connection        vector from a point on the top surface of the material source to        the sample point on the coating surface, is at least 30° and at        most 75° throughout the entire method,    -   applying at least one coating on the side of the base layer that        has the coating surface by means of the material source, wherein    -   the substrate holder during the coating process of the coating        is rotated around a substrate axis of rotation which runs along        the main extension direction of the rotating arm.

The idea underlying the described method here, particularly, is that auniform coating of the base layer can be achieved by exactly adjustingthe length of the rotating arm in such a manner that the normal angle isat least 30° and at most 75°. As a result, a conformable coating ofedges and/or corners of the base layer is enabled. Furthermore, theproduction of crack-free and thus hermetically sealed coatings isenabled.

According to at least one embodiment of the method, the substrate holderis additionally rotated around an overall axis of rotation, which runsalong the main coating direction of the material source within theproduction tolerances. Preferably, rotation is effected throughout theentire coating process. Irregularities in the material flow vaporizedfrom the material source can be compensated by means of the rotationaround the overall axis of rotation.

By means of the simultaneous rotation around the substrate axis ofrotation and the overall axis of rotation, a uniform, conformablecoating is achieved in the present case. By means of the rotation aroundthe substrate axis of rotation, it is particularly possible to coat theside surfaces of the base layer in a uniform fashion. As alreadydescribed with regards to the rotation-dependent change of the normalangle, the distance of the base layer to the material source changesduring rotation around the substrate axis of rotation. Thus, whencoating two base layers, for example, which may initially have adifferent distance to the material source, irregularities in the coatingthickness due to the different distance can be compensated.

Such irregularities in the coating thickness could be traced back to thefact that the material flow released by the material source decreasesquadratically along with a decreasing distance to the material source(so-called distance-square law). Thus, a first base layer, which isinitially closer to the material source than a second base layer, isfarther away from the material source than the second base layer at alater point of time. Furthermore, due to rotation, it is possible thatthe side surfaces of the base layer are coated in a uniform manner,since in each case another side surface faces the material source duringrotation around the substrate axis of rotation. The respectiveorientation of each of the side surfaces relative to the materialsource, in particular to the main coating direction of the materialsource, is thus varied during the coating process by the rotation aroundthe substrate axis of rotation.

In addition, the rotation around the overall axis of rotation causes acompensation of irregularities in the material flow released by thematerial source. Ideally, the material flow would have a rotationsymmetry relative to the main coating direction, and thus relative tothe overall axis of rotation. However, material flows of real materialsources deviate from the rotation symmetry. The deviation is compensatedby the rotation around the overall axis of rotation.

According to at least one embodiment of the method, rotation around thesubstrate axis of rotation is effected with a first rotary frequency,and rotation around the overall axis of rotation is effected with asecond rotary frequency. Here, the first rotary frequency is greaterthan the second rotary frequency. For example, the first rotaryfrequency is at least four times, preferably 5.25 times greater than thesecond rotary frequency. In other words, rotation around the substrateaxis of rotation is significantly more rapid than the rotation aroundthe overall axis of rotation. The different selection of rotaryfrequencies accounts for the fact that the irregularities in the coatingthickness, which could result from a different orientation of the sidesurfaces to the material source, are significantly greater than theirregularities in the coating thickness, which could result from aninhomogeneity in the material flow of the material source.

According to at least one embodiment of the method, an arbitrary pointon the coating surface is selected as the sample point. In other words,the surface normal of the coating surface defining the normal angle mayrun through any point on the coating surface of the base layer. As aresult, each normal angle of any surface normal of the coating surfacethrough an arbitrary sample point on the coating surface with a samplevector fulfils the above condition throughout the entire coating timethat the normal angle is at least 30° and at most 75°.

According to at least one embodiment of the method, a plurality of baselayers with in each case one coating surface are arranged on the topsurface of the substrate holder. Each normal angle of each coatingsurface of each of the plurality of base layers is at least 30° and atmost 75°.

According to at least one embodiment of the method, the length of therotating arm is adjusted in such a manner that the length is at least100 mm and at most 700 mm. The selection of the length of the rotatingarm depends on the size of the coating apparatus and scaled therewith.Preferably, the length is at least 200 mm and at most 400 mm and verypreferably at least 220 mm and at most 300 mm. In this case, a selectionof the length of the rotating arm in this region allows the provision ofboth a normal angle, which is at least 30°, and a great number ofsubstrates, without that they touch one another due to limited space,and/or a top surface of a substrate holder is shadowed by the materialflow from the material source.

According to at least one embodiment of the method, the coatingcompletely covers over all edges and corners of the base layer facingaway from the substrate holder. In other words, the base layer iscovered by the coating conformably and without gaps. The base layer isno longer freely accessible on the external surfaces facing away fromthe substrate holder, i.e. on its coating surface and all side surfaces,after applying the coating. Just as well, the edges and corners of thebase layer are completely covered. Here and in the following, an edge ofthe base layer is a place where a side surface encounters the coatingsurface. Here and in the following, a corner of the base layer is aplace where two side surfaces and the coating surfaces coincide. Asquare-shaped base layer comprises four edges facing away from thesubstrate holder and four corners facing away from the substrate holder,for example. A truncated cone shaped base layer comprises merely oneedge facing away from the substrate holder, where the shell surfaceencounters the top surface of the truncated cone, for example. Here, theterms “edge” and/or “corner” are not to be understood as strictlygeometrical terms, but rather include within the production tolerancesrounded edges and/or corners.

According to at least one embodiment of the method, the substrate holderhas a disk-shaped design. The top surface and/or the bottom surface ofthe substrate holder then have the shape of a circle. Here, the radiusof the circular top surface and/or the circular bottom surface of thesubstrate holder is at least 30 mm and at most 350 mm. Preferably, theradius is at least 40 mm and at most 200 mm, particularly preferably atmost 120 mm. Here, the substrate axis of rotation runs through a centerpoint of the circular top surface and/or the circular bottom surface.Here, the terms “circle”, “circular”, “disk”, “disk-shaped”, “radius”and “center point” are not to be understood as exact geometric terms butrather as information that is to be interpreted within the productiontolerances. For example, the top surface and/or the bottom surface mayhave the shape of an almost circular ellipsis, wherein the numericeccentricity of the ellipsis may be at most 10%.

Here, it is possible that the contour of the substrate holder in a planview can be merely approximated by the shape of a circle. For example,the substrate holder may have the shape of a clover-leaf, in particularof a four-leaf clover, in a plan view. The shape of the clover-leaf canthen be encircled with a circle in a plan view. Here, in a plan view,the substrate holder may have at least one axis of symmetry, preferablyat least two axes of symmetry and particularly preferably at least fouraxes of symmetry. The substrate holder may have an extension of at least30 mm and at most 350 mm in at least one spatial dimension.

According to at least one embodiment of the method, at least twosubstrates and at least two rotating arms are provided. Preferably, ineach case a plurality of base layers is arranged on each of thesubstrates. The two substrates are in each case arranged on one rotatingarm, wherein each substrate holder is uniquely assigned to one rotatingarm. Preferably, the two rotating arms have an equal length within theproduction tolerances. However, it is also possible that the rotatingarms have a different length. This enables a different coating of thebase layers arranged on the two substrates, for example.

The two substrates each rotate around a substrate axis of rotation,through which the main extension direction of the respective rotatingarm runs, respectively. Preferably, both substrates rotate with the samefirst rotary frequency. However, it is also possible that the rotaryfrequencies of the two substrates differ from one another. This may bethe case, for example, if structurally different coatings are to beapplied to the base layers of the two substrates.

According to at least one embodiment of the method, the at least twosubstrates and the material source are not arranged on a common surfaceof a sphere. For example, the two substrates may be arranged on a commonsurface of a sphere, with the material source not being arranged on thiscommon surface of a sphere. Thus, it is not possible to define a spherein space on the surface of which both the two substrates and thematerial source are arranged at least in places.

In contrast to this, the substrates and the material source of aso-called Knudsen gear or planetary gear are arranged on a commonsurface of a sphere. In contrast to the method described herein, acoating method with such a Knudsen gear or planetary gear, respectively,comes with the disadvantage that no uniform covering of the edge(s) ofthe base layer with the coating results, but rather an asymmetry of theover-coating depending on the orientation and the position of the baselayers on the substrate holder. Moreover, gaps and cracks develop in thecoating, in the area of the edges to be coated, during the coatingprocess, using such a Knudsen gear or planetary gear, respectively.

Furthermore, an optoelectronic semiconductor component is provided. Acoating of the optoelectronic semiconductor component is preferablyproduced with the method described herein. That is, all featuresdisclosed for the method are also disclosed for the coating of theoptoelectronic semiconductor component and vice versa.

According to at least one embodiment of the optoelectronic semiconductorcomponent, the component comprises at least one base layer with acoating surface and two radial side surfaces disposed opposite oneanother. Furthermore, the base layer comprises two tangential sidesurfaces opposite one another, which run transversely or perpendicularlyto the radial side surfaces within the production tolerances.Preferably, in each case two radial side surfaces adjoin one tangentialside surface and vice versa. For example, the base layer is designed inthe shape of a cuboid or a truncated pyramid. The radial side surfacesmay then be arranged parallel to one another within the productiontolerances. Just as well, the tangential side surfaces may be arrangedparallel to one another within the production tolerances. Here, theradial side surfaces can be the side surfaces which face toward or faceaway from the substrate axis of rotation, respectively. The tangentialside surfaces can be the side surfaces which comprise at least onesurface normal, which run along the direction of rotation of the firstrotary frequency.

The base layer further comprises a bottom surface and edges and cornersfacing away from the bottom surface, where the tangential respectivelyradial side surfaces encounter the coating surface.

According to at least one embodiment of the optoelectronic semiconductorcomponent, the component comprises at least one coating. The coatingcompletely covers the edges and corners of the base layer. In otherwords, the coating covers the base layer conformably. For example, thecoating may be an insulating layer of the optoelectronic semiconductorcomponent. Furthermore, the coating may be a reflective layer and/or anelectrically conductive connection layer of the optoelectronicsemiconductor component. It is also possible that the coating is asemiconductor layer of the optoelectronic semiconductor component. Bymeans of a conformable coating, for example, the base layer can behermetically sealed toward the outside and be protected against theintrusion of air and/or liquids. Furthermore, a conformable coating canbe used for the production of highly-reflective layers.

The material of the coating may have a high purity. For example, thequantity proportion of the impurity atoms in the coating is at most 3%,preferably at most 1%, of the atoms of the material of the coating.Inter alia, the production by means of vapor deposition can besubstantiated via the purity of the material of the coating. The featureaccording to which the coating has been produced by means of vapordeposition is thus an object feature that can be verified on thefinished component.

According to at least one embodiment of the optoelectronic semiconductorcomponent, this component comprises at least a base layer having acoating surface, two radial side surfaces opposite one another, twotangential side surfaces opposite one another, which run transversely orperpendicular to the radial side surfaces within the productiontolerances, a bottom surface and edges and corners facing away from thebottom surface, and at least one coating, wherein the coating completelycovers the edges and corners of the base layer.

According to at least one embodiment of the optoelectronic semiconductorcomponent, the coating comprises external surfaces. The coatingthickness on at least one radial side surface of the base layer is atleast 25% of the coating thickness on the coating surface of the baselayer. In other words, the coating thickness of the coating has auniform design. Here and in the following, the coating thickness on aradial side surface and/or on a tangential side surface and/or on thecoating surface of the base layer is the minimum distance of at leastone of the external surfaces of the coating to the radial side surfaceand/or the coating surface.

Furthermore, by means of a comparison between the coating thickness onat least one radial side surface and the coating thickness on thecoating surface, the normal angle selected during the method can beverified. Thus, the coating thickness on the radial side surfacesincreases along with an increasing normal angle. In a normal angle of75°+/−5°, the coating thickness on the at least one radial side surfacemay correspond to the coating thickness on the coating surface. Thus, anoptimal uniform coating may result with this angle. However, in thepresent case, it turned out that under consideration of further factors,such as the number of the base layers attached on the substrate holderand/or the size of the substrate holder, an optimum in uniformity canalready be achieved as from a normal angle of 30°.

According to at least one embodiment of the optoelectronic semiconductorcomponent, the coating thickness on a tangential side surface of thebase layer is at least 30% of the minimum distance of the externalsurfaces to the coating surface of the base layer. Thus, the tangentialside surfaces can be coated in a more uniform manner than the radialside surfaces.

According to at least one embodiment of the optoelectronic semiconductorcomponent, the coating in the area of the radial side surfaces and/orthe tangential side surfaces of the base layer is free from crackscompletely penetrating the layer. In other words, crack-free coatingsand/or hermetically sealed coatings can be produced by the method forproducing a coating as provided herein.

In the following, the method for producing a coating described herein,as well as the optoelectronic semiconductor component described herein,having a coating that has been produced by means of a method will bedescribed in greater detail with regards to exemplary embodiments andthe associated Figures.

FIG. 1 shows an exemplary embodiment of an arrangement for performing amethod described herein by means of a schematic side view.

FIGS. 2, 3 and 4 show schematic sketches for explaining a methoddescribed herein in greater detail.

FIG. 5 shows an angular dependence of the coating thickness of a coatingfor the explanation of a method described herein.

FIG. 6 shows a coating thickness of a coating as a function of thelength of the rotating arm for the explanation of a method describedherein.

FIGS. 7 and 8 show the change over time of geometric relations, as wellas of the coating thickness for the explanation of a method describedherein.

FIGS. 9A and 9B show exemplary embodiments of an optoelectronicsemiconductor component described herein by means of schematic sectionalillustrations and scanning electron microscope (SEM) images.

Like, similar or equivalent elements are provided with like referencenumerals throughout the figures. The figures and the dimensionalrelations of the elements illustrated in the drawings are understood tonot be made to scale. Rather, individual elements can be illustrated inan exaggerated manner for a better illustration and/or a betterunderstanding.

By means of the schematic side view of FIG. 1, a method for producing acoating is explained in greater detail. The side illustration shows asketched arrangement for the production of a coating 22. The arrangementcomprises a material source 4 with a vaporization surface 4 a. Thematerial source 4 comprises a main coating direction Z. The main coatingdirection Z forms a Cartesian coordinate system X, Y, Z together withthe two directions X, Y spanning the plane of the vaporization surface 4a.

Furthermore, the arrangement comprises a rotation holder 51, a fasteningarm 52 and a rotary joint 53. The rotary joint 53 is fixed to therotation holder 52 by means of the fastening arm 52. A rotating arm 3 isattached to the rotary joint 53. The rotating arm 3 has a length 3L inits main extension direction. A substrate holder 1 is attached to therotating arm 3. A virtual extension of the rotating arm 3 through thesubstrate holder 1 runs preferably through a center of mass of thesubstrate holder 1. A second substrate holder 1 on a second rotating arm3 is illustrated on the right side of FIG. 1. Here, the structure is thesame as that on the left side of FIG. 1.

The entire arrangement including the rotation holder 51, fastening arm52, rotary joint 53, rotating arm 3 and substrate holder 1 rotates witha second rotary frequency ω₂ around an overall axis of rotation, whichruns along the main coating direction Z of the material source 4.Furthermore, the rotating arm 3 performs a self rotation with a firstrotary frequency ω₁ around a substrate axis of rotation 11, which runsalong the main extension direction of the rotating arm 3.

The substrate holder 1 comprises a top surface 1 a. A base layer 2 isattached on the top surface 1A. A sample point 2 p is marked on acoating surface 2 a of the base layer 2. In the present case, the samplepoint 2 p is selected, such that a virtual extension of the substrateaxis of rotation 11 running along the rotating arm 3 runs through thesample point 2 p. However, the sample point 2 p can be selectedarbitrarily on the coating surface 2 a of a base layer 2.

The connection vector from a point 4 m on the vaporization surface 4 aof the material source 4 to the sample point 2 p forms the sample vector42. A normal angle φ is enclosed by the sample vector 42 and a surfacenormal 291 through the sample point 2 p. The normal angle φ is set bymeans of a variation of the length 3L of the rotating arm 3. Here, thenormal angle φ is at least 30° and at most 75°. Preferably, the normalangle φ is at least 40° and at most 60°.

According to the schematic sketch of FIG. 2, a method for producing acoating is explained in greater detail. FIG. 2 shows the material source4 with the vaporization surface 4 a and a point 4 m on the vaporizationsurface 4 a of the material source 4. The main coating direction Z ofthe material source 4 runs through the point 4 m on the vaporizationsurface 4 a. The sketch also shows the substrate holder 1, which isarranged on the rotating arm 3, along the main extension direction ofwhich runs the substrate axis of rotation 11. The rotating arm 3 rotateswith the first angular velocity ω₁ around the substrate axis of rotation11.

The base layer 2 is arranged on the top surface 1 a of the substrateholder 1. The base layer 2 comprises a coating surface 2 a as well asradial side surfaces 2 r 1, 2 r 2 and tangential side surfaces 2 t 1, 2t 2. The positive radial side surface 2 r 1 can be found on the side ofthe base layer 2 facing the rotating arm 3 and the negative radial sidesurface 2 r 2 can be found on the side of the base layer 2 facing awayfrom the rotating arm 3. The positive tangential side surface 2 t 1precedes the negative tangential side surface 2 t 2 (not shown in FIG.2) in the rotation direction around the substrate axis of rotation 11.In other words, at least one surface normal of the positive tangentialside surface 2 t 1 runs parallel to the rotation direction and at leastone surface normal of the negative tangential side surface 2 t 2 runsantiparallel to the rotation direction. The radial side surfaces 2 r 1,2 r 2 are located opposite one another. Just as well, the tangentialside surfaces 2 t 1, 2 t 2 are located opposite one another (not shownin FIG. 2). Within the production tolerances, the tangential sidesurfaces 2 t 1, 2 t 2 run perpendicular to the radial side surfaces 2 r1, 2 r 2.

A sample point 2 p is located on the coating surface 2 a of the baselayer 2. The sample point 2 p has a distance 32 from the rotating arm 3.Furthermore, the base layer 2 has a medium distance D to the materialsource.

The sample vector 42, derived from the connection vector from point 4 mon the vaporization surface 4 a of the material source 4 to the samplepoint 2 p on the coating surface 2 a of the base layer 2, encloses amaterial angle θ with the main coating direction Z. Just as well, thesample vector 42 encloses a normal angle φ with the surface normal 291through the sample point 2 p.

The radial vector 292 runs along the coating surface 2 a. The radialvector 292 is perpendicular to the surface normal 291 through the samplepoint 2 p. The radial vector 292 encloses a radial angle α with thesample vector 42. The surface normal 291, the radial vector 292 and atangential vector 293 (not shown here) form a three-dimensionalCartesian coordinate system, which is rotated relative to the Cartesiancoordinate system X, Y, Z defined by the material source 4. Thetangential vector 293 runs perpendicular to the surface normal 291 andthe radial vector 292 and runs out of the image plane of FIG. 2.

At the point of time shown in FIG. 2, during the coating process, thenegative radial side surface 2 r 2 is oriented toward the materialsource 4 and can thus be directly coated, while the positive radialsurface 2 r 1 is oriented away from the material source 4 and can thusonly be poorly coated or not coated at all. The positive radial sidesurface 2 r 2 can thus be coated better with the material of thematerial source 4. At a later point in time, e.g. after a half turn ofthe substrate holder 1 around the substrate axis of rotation 11, thepositive radial side surface 2 r 1 will be oriented toward the materialsource 4 and the negative radial side surface 2 r 2 will be orientedaway from the material source 4. Thus, a uniform coating of the radialside surfaces 2 r 1, 2 r 2 will be enabled by the rotation around thesubstrate axis of rotation 11.

According to the schematic illustration of FIG. 3, a method forproducing a coating 22 described herein is explained in greater detail.Calculated time-dependent positions of sample points 2 p 1, 2 p 2 on thecoating surface 2 a of the base layer 2 in the coordinate system X, Y, Zdefined by the material source 4 are illustrated. The point of origin isderived from a point 4 m on the vaporization surface 4 a of the materialsource 4.

The first sample point 2 p 1 is arranged, such that distance 32 to thesubstrate axis of rotation 11 is great. The second sample point 2 p 2 isarranged such that it only deviates slightly from the position of thesubstrate axis of rotation 11, i.e. it has an infinitesimally smalldistance 32 to the substrate axis of rotation 11. The time-dependentposition of the first sample point 2 p 1 is thus influenced by both therotation around the substrate axis of rotation 11 and the rotationaround the overall axis of rotation. The time-dependent position of thesecond sample point 2 p 2 is merely influenced by the rotation aroundthe overall axis of rotation.

This different influence can for example be discerned from the greatertime variation of the position of the first sample point 2 p 1 comparedover the time variation of the position of the second sample point 2 p2. The first sample point 2 p 1 performs a double rotation around thematerial source 4. The first sample point 2 p 1 thus has a more complexmovement than the second sample point 2 p 2 and includes a greatervariation of normal angles φ with the sample vector 42.

Furthermore, FIG. 3 shows a sketched three-dimensional illustration ofthe rotated Cartesian coordinate system 291, 292, 293 spanned by thesurface normal 291, the radial vector 292 and the tangential vector 293.The tangential vector 293 runs parallel to the rotation direction of therotation around the substrate axis of rotation 11 with the first rotaryfrequency ω₁. The radial vector 292 runs parallel to the coating surface2 a, on which the sample point 2 p 1, 2 p 2 is located.

According to the sketch of FIG. 4, a method for producing a coating isexplained in greater detail. The sketch shows a sample point 2 p at anarbitrary point in time during the coating process. Furthermore, therotating arm 3 and the substrate axis of rotation 11 coinciding with therotating arm 3 is shown. The rotated Cartesian coordinate system 291,292, 293 is illustrated at the position of the sample point 2 p.

The surface normal 291 encloses the normal angle φ with the samplevector 42. The radial vector 292 encloses a radial angle α with thesample vector 42. The tangential vector 293 encloses a tangential angleβ with the sample vector 42.

Due to the rotation around the substrate axis of rotation and/or theoverall axis of rotation, the radial angle α, the tangential angle β andthe normal angle φ vary during rotation of the substrate holder 1.

According to the calculated angle dependence of the normalized coatingthicknesses 61, 62 of FIG. 5, a method for producing a coating isexplained in greater detail. What is illustrated is the coatingthickness |d|, normalized to the coating thickness on the coatingsurface 2 a, as a function of the normal angle φ in degree. FIG. 5 showsthe normalized coating thickness 61 on the coating surface 2 a and thenormalized medium coating thickness 62 on the side surfaces 2 r 1, 2 r2, 2 t 1, 2 t 2 of the base layer 2, which represents a medium value ofthe respective normalized coating thicknesses on the respective sidesurfaces 2 r 1, 2 r 2, 2 t 1, 2 t 2.

For the calculation of the coating thickness, it was assumed that thematerial flow I released by the material source 4 has the followingproportional dependence on the material angle θ and the medium distanceD of the base layer 2 from the material source 4:

I(θ, D)˜cos(θ)^(n)*D⁻²,

with the material parameter n depending on the material of the materialsource 4. For example, n=3 is true for the case of gold. Thus, arotation-symmetrical cosine-dependence in conjunction with thedistance-square law is assumed for the material flow 4.

The normalized medium coating thickness 62 on the side surfaces 2 r 1, 2r 2, 2 t 1, 2 t 2 increases along with an increasing normal angle φ. Amaximally uniform coating is achieved with a normal angle φ ofapproximately 72.4°. At this angle, the normalized medium coating 62 onthe side surfaces 2 r 1, 2 r 2, 2 t 1, 2 t 2 and the normalized coatingthickness 61 on the coating surface 2 a have the same size. Thus, at theangle of 72.4°, a maximally conformable and homogenous coating of thebase layer 2 can be expected.

However, it turned out that a sufficiently homogenous and conformablecoating of the base layer 2 can already be achieved from a normal angleof at least 30°. In addition, a higher number of base layers 2 ispossible with smaller normal angles φ, since the substrate holders 1 canbe located farther away from the material source 4 and thus a greaternumber of substrate holders 1 and/or greater substrate holders 1 can beused in conjunction with one single material source 4.

According to the calculated normalized coating thicknesses 711, 712,721, 722, 731, 732 of FIG. 6, a method for producing a coating describedherein is explained in greater detail. In contrast to FIG. 5, thenormalized coating thickness on the respective side surfaces 2 r 1, 2 r2, 2 t 1, 2 t 2 is applied, respectively, in FIG. 6. The normalizedcoating thickness 711, 712, 721, 722, 731, 732 is indicated as afunction of the length 3L of the rotating arm 3.

The points show as follows: the normalized coating thickness 711, 712 onthe positive radial side surface 2 r 1, the normalized coating thickness721, 722 on the negative radial side surface 2 r 1, the normalizedcoating thickness 731, 732 on the tangential side surfaces 2 t 1, 2 t 2and the normalized coating thickness 61 on the coating surface 2 a. Thenormalized coating thicknesses 731, 732 for the tangential side surfaces2 t 1, 2 t 2 are not separately shown for the positive 2 t 1 and thenegative 2 t 2 tangential side surface, since the normalized coatingthicknesses of the two tangential side surfaces 2 t 1, 2 t 2 are thesame. The filled data points 711, 721 and 731 respectively show thenormalized coating thickness for a substrate holder having a diameter of150 mm, while the non-filled points 712, 722, 732 respectively show thecalculations of the normalized coating thickness for a substrate holderhaving a diameter of 50 mm.

Along with an increasing length 3L, the normal angle φ increases andthus the normalized coating thickness on the side surfaces 2 r 1, 2 r 2,2 t 1, 2 t 2, also increase and, consequently, the uniformity of thecoating thickness. In particular the tangential side surfaces 2 t 1, 2 t2 can be coated homogeneously and conformably. At a length 3L ofapproximately 460 mm, the optimum normal angle φ of approximately 72.4°is achieved.

According to the time-dependent course illustrated in FIG. 7, a methoddescribed herein is explained in greater detail. What is illustrated arethe calculations of the normal angle φ, the tangential angle β1, β2, theradial angle α1, α2 as well as the material angle θ as a function of therotation time t in seconds. Here, the rotation of the substrate holderis accounted for by the specification of a first tangential angle β1, asecond tangential angle β2, a first radial angle α1 and a second radialangle α2. The sample vector 42 encloses the first tangential angle β1respectively the first tangential angle α1 with the tangential vector293 respectively with the radial vector 292. Furthermore, the samplevector 42 encloses the second tangential angle β2 respectively thesecond tangential angle α2 with the mathematically inverse, i.e.negative tangential vector 293 respectively the mathematically inverse,i.e. negative radial vector 292.

Furthermore, the time-dependent length of the sample vector 42 inmillimeters is illustrated in the time-dependent course of FIG. 7. Arotation around the substrate axis of rotation 11 terminates after 120seconds. The first rotary frequency ω₁ is thus 1/120 Hz. Accordingly,the time-dependent course is repeated after 120 seconds.

The angles φ, α1, α2, β1, β2, θ and the length of the sample vector 42change during the rotation. The normal angle φ is at least 30° and atmost 75° throughout the entire rotation. The normal angle φ variesbetween 125° and 155°, corresponding to the acute angles 35° and 65°,for example.

According to the time-dependent deposition rate of FIG. 8, a method forproducing a coating 22 described herein is explained in greater detail.Here, the deposition rate is the rate with which material of thematerial source 4 is deposited on the respective surface 2 a, 2 r 1, 2 r2, 2 t 1, 2 t 2 of the base layer 2. The time-dependent deposition rateon the base layer 2 in arbitrary units (a.u.) as a function of therotation time t in seconds is illustrated. FIG. 8 shows the depositionrate 81 on the coating surface 2 a, the deposition rate 821 on thepositive radial side surface 2 r 1, the deposition rate 822 on thenegative radial side surface 2 r 2, the deposition rate 831 on thepositive tangential side surface 2 t 1 and the deposition rate 832 onthe negative tangential side surface 2 t 2.

The respective deposition rate of the coating changes over time. Thus,initially, the deposition rate 81 on the coating surface 2 a and thedeposition rate 821 on the positive radial side surface 2 r 2 aremaximal. Along with the rotation around the substrate axis of rotation11 the orientation of the side surfaces 2 r 1, 2 r 2, 2 t 1, 2 t 2 tothe material source 4 is changed. Accordingly, the deposition rate 832on the negative tangential side surface 2 t 2 increases, for example,while the deposition rate 81 on the coating surface 2 a decreases. Aftera half turn, at the time t=60 s, the deposition rate 822 on the negativeradial surface 2 r 2 is maximal. From a point in time of about t=80 s,the deposition rate 831 on the positive tangential side surface 2 t 2and the deposition rate 81 on the coating surface 2 a increase. Beforethe end of the rotation, from a point in time of about t=100 s, thedeposition rate 811 on the positive radial surface 2 r 1 increasesagain. An integral over the respective curves then represents thecoating thicknesses, according to FIGS. 5 and 6.

According to the SEM images of FIGS. 9A and 9B, the exemplaryembodiments of the optoelectronic semiconductor component describedherein are explained in greater detail. FIG. 9A shows the optoelectronicsemiconductor component with a coating 22, which has not been producedby means of a method described herein. FIG. 9B shows an optoelectronicsemiconductor component with a coating 22, which has been produced bymeans of a method described herein.

In the optoelectronic semiconductor component of FIG. 9A, cracks 221 canbe discerned on the edges of the base layer 2 to be coated. These cracksin the coating 22 are not present in the optoelectronic semiconductorcomponent of FIG. 9B. Furthermore, it is clearly discernable in FIG. 9Bthat the optoelectronic semiconductor component respectively the coating22 has been produced with a method described herein. Thus, the coatingthickness 223 of the coating 22 on the side surfaces 2 r 1, 2 r 2 isapproximately half the size of the coating thickness 224 on the coatingsurface 2 a of the base layer 2. This leads to the conclusion that anormal angle φ of approximately 45° was used.

The invention is not limited to the exemplary embodiments by means ofthe description with regards to these exemplary embodiments. Theinvention rather comprises each new feature, as well as each combinationof features, which particularly includes any combination of features inthe patent claims, even if said feature or said combination of featuresis not explicitly indicated in the patent claims or exemplaryembodiments per se.

The present application claims priority of German application DE 10 2014108 348.2, the disclosure of which is incorporated herein by reference.

1. A method for producing a coating comprising the steps: providing amaterial source having a top surface and a main coating direction,providing a substrate holder having a top surface, providing at leastone base layer having a coating surface facing away from the substrateholder on the top surface of the substrate, attaching the substrateholder to a rotating arm, which has a length along a main extensiondirection of the rotating arm, adjusting the length of the rotating armin such a manner that a normal angle, which is enclosed by the surfacenormal of the coating surface of the base layer through a sample pointon the coating surface and a sample vector, derived from the connectionvector from a point on the top surface of the material source to thesample point on the coating surface, is at least 30° and at most 75°throughout the entire method, applying at least one coating to that sideof the base layer, which comprises the coating surface by means of thematerial source, wherein during the coating process of the coating, thesubstrate holder is rotated around a substrate axis of rotation runningalong the main extension direction of the rotating arm.
 2. The methodaccording to claim 1, wherein the substrate holder is additionallyrotated around an overall axis of rotation, which runs along the maincoating direction of the material source within the productiontolerances, the rotation around the substrate axis of rotation iseffected with a first rotary frequency and the rotation around theoverall axis of rotation is effected with a second rotary frequency,wherein the first rotary frequency is greater than the second rotaryfrequency, at least two substrates are provided, and the at least twosubstrates and the material source are not arranged on a common surfaceof a sphere.
 3. The method according to claim 1, wherein the substrateholder is additionally rotated around an overall axis of rotation, whichruns along the main coating direction of the material source within theproduction tolerances.
 4. The method according to claim 3, wherein therotation around the substrate axis of rotation is effected with a firstrotary frequency and the rotation around the overall axis of rotation iseffected with a second rotary frequency, wherein the first rotaryfrequency is greater than the second rotary frequency.
 5. The methodaccording to claim 1, wherein an arbitrary point on the coating surfaceis selected as the sample point on the coating surface.
 6. The methodaccording to claim 1, wherein a plurality of base layers with aplurality of coating surfaces is arranged on the top surface of thesubstrate holder.
 7. The method according to claim 1, wherein the lengthof the rotating arm is at least 100 mm and at most 700 mm.
 8. The methodaccording to claim 1, wherein the length of the rotating arm is at least200 mm and at most 400 mm.
 9. The method according to claim 1, whereinthe coating completely covers all edges and corners of the base layerfacing away from the substrate holder.
 10. The method according to claim1, wherein the substrate holder has a disk-shaped design, wherein theradius of the circular surface area of the disk is at least 30 mm and atmost 350 mm.
 11. The method according to claim 1, wherein the substrateholder has an extension of at least 30 mm and at most 350 mm in at leastone dimension.
 12. The method according to claim 1, wherein at least twosubstrates are provided.
 13. The method according to claim 12, whereinthe at least two substrates and the material source are not arranged ona common surface of a sphere.
 14. An optoelectronic semiconductorcomponent, comprising: at least one base layer having a coating surface,two radial side surfaces opposite one another, two tangential sidesurfaces opposite one another, which run transversely or perpendicularlyto the radial side surfaces within the production tolerances, a bottomsurface and edges and corners facing away from the bottom surface, andat least one coating, wherein the coating completely covers the edgesand corners of the base layer.
 15. The optoelectronic semiconductorcomponent according to claim 14, wherein the coating has externalsurfaces, wherein the minimum distance of the external surfaces to atleast one radial side surface of the base layer is at least 25% of theminimum distance of the external surfaces to the coating surface of thebase layer.
 16. The optoelectronic semiconductor component according toclaim 14, wherein the coating has external surfaces, wherein the minimumdistance of the external surfaces to at least one tangential surface ofthe base layer is at least 25% of the minimum distance of the externalsurfaces to the coating surface of the base layer.
 17. Theoptoelectronic semiconductor component according to claim 14, whereinthe coating in the region of the radial side surfaces and/or tangentialside surfaces of the base layer is free of cracks penetrating entirelythrough the coating.
 18. An optoelectronic semiconductor component,comprising: at least one base layer having a coating surface, two radialside surfaces opposite one another, two tangential side surfacesopposite one another, which run transversely or perpendicularly to theradial side surfaces within the production tolerances, a bottom surfaceand edges and corners facing away from the bottom surface, and at leastone coating, wherein the coating completely covers the edges and cornersof the base layer and has external surfaces, wherein the minimumdistance of the external surfaces to at least one radial side surface ofthe base layer is at least 25% of the minimum distance of the externalsurfaces to the coating surface of the base layer and/or the minimumdistance of the external surfaces to at least one tangential surface ofthe base layer is at least 25% of the minimum distance of the externalsurfaces to the coating surface of the base layer.